docs: def split_class_dir_fixed(class_dir, output, fixed, seed):
      """Splits one very class folder
      """
      files = setup_files(class_dir, seed)
  
      assert len(files) > sum(fixed)
  
      split_train = len(files) - sum(fixed)
      split_val = split_train + fixed[0]
  
      li = split_files(files, split_train, split_val, len(fixed) == 2)
      copy_files(li, class_dir, output)
      return len(files)